We have numerically calculated the variation along the thickness of the sample, for a photorefractive material bismuth silicon oxide, of the intensities of two interfering beams in the steady state with high modulation depths. We obtained this variation under different applied electric fields (2.5, 5.0, and 10 kV/cm). The coupling gain coefficient Γ sinφ of the beams was calculated by solving the material rate equations for each value of the applied field. We found that this coupling coefficient is not linear with the applied field. With the variation of the beams, we obtained the light and index fringe profiles which are predicted as not parallel, in contraposition with the linear regime prediction. We also present the dependence of these profiles on the applied field.

• Received 19 February 1998

DOI:https://doi.org/10.1103/PhysRevB.58.9591